Homocystinuria Without Methylmalonic Aciduria, also known as functional methionine synthase deficiency, is related to homocystinuria-megaloblastic anemia, cblg complementation type and homocystinuria-megaloblastic anemia, cble complementation type. An important gene associated with Homocystinuria Without Methylmalonic Aciduria is MTRR (5-Methyltetrahydrofolate-Homocysteine Methyltransferase Reductase). Affiliated tissues include bone marrow and bone, and related phenotypes are hypotonia and megaloblastic bone marrow